There is all sorts of reality TV.
There is the variety Jersey Shore, Survivor, the Khardassians (or however you spell that) which really is mostly scripted and pre-thought of, they are just letting scenarios play out. Or something is going to happen in real life, and they built a script around it.
There is things like Pawn Stars, which is partly scripted (things like "I can race better than you", followed by a race at a local kart hall), and partly because of people that participate in the show by just being there/showing up. But obviously that is also partly scripted, that is.... the items get chosen, the people must want to participate, etc.
Then there is the American Idol type variety, which has a lot of user interaction, such as voting. Other types are purely judge only, or only have a voting round in the final.
Then there is COPS. I'd call this one a true reality show, as it follows cops as they are doing their rounds, and nothing is scripted. Faces of suspects are often blurred out ,etc.
Shows like Mythbusters are in a category of their own, but I would not actually call that reality TV at all, it is merely just a entertainment show with a scientific approach where they test theories and myths.
But I think this is probably best discussed in TV Shows in a separate thread, not here. Let's just close with that everyone's perception of what is "reality" is different.
I have about five reality types:
CRAP: "Keeping Up With The Kardashians", "Teen Mom", etc...
COMPETITIVE: "American Idol", "Survivor", "Big Brother", "The X-Factor", "The Amazing Race", "Dancing With The Stars", "The Voice", "Duets", etc...
GAME SHOWS: "Wheel Of Fortune", "Jeopardy", etc...
GENERAL: "Pawn Stars", "Swamp People", etc.
A few could be in a class their own, but I try and keep it to five.